But come September, he’ll resurface on NBC weeknights at 10 — where viewers who found their lids drooping during his “Tonight Show” monologue can now (hopefully) remain alert for Jay’s entire prime-time show.

Still, the late-night landscape is losing another piece of its classic mosaic.

Like Steve Allen, Jack Paar and Johnny Carson before him, Jay put his own unique stamp on his “Tonight Show” turf, making an indelible impression with his sharp, topical monologues, classic skits (who can forget “The Dancing Itos” and “Jaywalking”?) and his self-deprecating, everyman demeanor that played so well to a diverse, tough-to-please audience.

He had the late-night touch, which ain’t easy — as Chevy Chase, Pat Sajak, Joey Bishop and Dick Cavett, to name only a few, learned the hard way.

Tonight’s departure didn’t have to happen. At 59, Jay is perfectly healthy. His work ethic is legendary. He loves to be on TV. He loves “The Tonight Show.”

His ratings are terrific — and have been for 14 years, since he needled Hugh Grant and brought America along for the ride. It’s been a mutual love affair ever since — with David Letterman’s “Late Show” as the spurned suitor.

But in their ultimate wisdom, NBC suits decided, five years ago, that Jay would leave now, to be succeeded by “Late Night” host Conan O’Brien.

It’s a corporate head-scratcher that many viewers, and Jay himself (although he’d never publicly say so), are still trying to comprehend.

Since the announcement, Jay’s been a good soldier, taking only the occasional potshot at NBC in his monologues and saying all the right things in countless interviews.

He even decided to stay at NBC, when he could have jumped to ABC or Fox — not for the money, but to prove a point and stick it to NBC. How sweet would it have been to exact TV revenge on his former employer?

The good news is that we’re only saying see you later to Jay, and not farewell.

He’ll return this fall with “The Jay Leno Show,” which sounds awfully like a retitled “Tonight Show” in an earlier time slot, complete with monologue and all the favorite sketches.

Still, it’s hard not to think back to 1995, and Jay’s defining “Tonight Show” moment with Hugh Grant. That’s when he turned to the chagrined actor, who’d just been arrested for soliciting a hooker, and asked incredulously, “What the hell were you thinking?”

You can almost hear America asking NBC that same question on Jay’s behalf.